Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W=map(int,input().split())
white=0
s=[]
for y in range(H):
    line=input()
    white+=line.count('.')
    s.append(list(line))

q = deque([(0,0,1)])
q_append=q.append
q_popleft=q.popleft
while q:
    x,y,l=q_popleft()
    if s[y][x]!='.':
        continue
    if x==W-1 and y==H-1:
        print(white-l)
        break
    s[y][x]='*'
    for d in [(1,0),(0,1),(-1,0),(0,-1)]:
        nx, ny=(x+d[0],y+d[1])
        if 0<=nx<W and 0<=ny<H:
            q_append((nx,ny,l+1))
else:
    print(-1)